An embodiment of such a steering system, viz. a catheter system, is disclosed in patent application US 2004/0254566 A1. The known system includes an apparatus comprising two rollers arranged parallel to each other and orthogonally to a catheter, which is gripped between these rollers. At least one of the rollers can be rotatably driven, and at least one of the said rollers is pressed elastically against the other to provide a frictional clamping of the interposed catheter. As a result of a roller's rotation in the clockwise or anti-clockwise direction the catheter moves longitudinally forwards or backwards respectively. Also, at least one of the two rollers can be axially moved in both of its axial directions in such a way that as a result of this axial movement the catheter gripped between the rollers is rotated rightwards or leftwards respectively about its own axis. The use of a single pair of rollers that are engaged with the catheter produces both the longitudinal forward and backward movements of the catheter, and its rightward or leftward rotation possibly simultaneously with the said longitudinal movement.
In the known apparatus rotations of the catheter are linked to movements of the catheter along the rollers' axial axes. A drawback thereof is that the number of rotations of the catheter is limited by the axial size of the rollers. In particular, if the catheter is continuously rotated the catheter will lose the contact with the rollers at certain moment as a consequence of its replacement along the rollers' axes and will not be gripped by rollers. Once this happens the movement of the catheter cannot be controlled by rollers any more.